1. Field of the Invention
The present invention relates to a device for correctly positioning a tip portion of a continuous form provided in a laser printer.
2. Description of the Related Art
In the operation of known laser printers, a sensitive drum is rotated in a sub-scanning direction while a laser beam is scanned along a main scanning direction, whereby a latent image to be printed is formed on the photosensitive drum, and the latent image is then transferred to a continuous form (fan-fold paper) fed along the sub-scanning direction. In this type of printer, the image transferred to the continuous form is fixed by a pair of fixing rollers disposed at a position apart by a predetermined interval from the photosensitive drum along the direction in which the continuous form is fed, and the printed continuous form is then discharged from the printer.
In this kind of laser printer, a printing process is carried out for each one page, and thus the space between the photosensitive drum and a pair of fixing rollers is set to correspond to a single page of the continuous form, and the printing of the form is carried out in such a manner that images as printed are aligned with ruled lines on the continuous form. Therefore, when the continuous form is fed in the laser printer, the tip portion of the continuous form must be forwarded and positioned so that the continuous form is set to a predetermined position. Accordingly, a tip sensor for sensing a position of the tip portion of the continuous form is provided at a point midway in a passage through which the continuous form is fed and near the fixing rollers.
When, however, a new continuous form is set to the printer, and the tip portion of the continuous form is positioned when the temperature of the fixing rollers waiting for a next printing process is high, since the tip portion of the continuous form is located approximately just under a heat roller of the fixing rollers, the tip portion is heated by the heat roller, and thus is curled, deteriorated in quality, and often burnt, and accordingly, a paper jam is apt to occur.